1. Field of the Invention
The present invention relates to high-frequency signal receivers and, more particularly, relates to a waveguide in which two probes are provided to increase receiving efficiency.
2. Description of the Background
Systems for receiving linearly polarized electromagnetic signals are well known and are now becoming increasingly important with the proliferation of satellite transmitted signals. An important feature of any such signal receiver is the shape and orientation of the receiver antenna probe, which typically is arranged within and near the closed end of a circular waveguide employed in the signal receiver. The signals received by such a waveguide and probe arrangement are fed to a low-noise amplifier (LNA) and then further processed in a conventional fashion. Frequently, provision is made to rotate the probe in the waveguide using a rotary drive mechanism to permit the probe to receive various individual polarizations of the incident signal. An example of a probe for use in such a rotating system is set forth in my U.S. Pat. No. 4,414,516 having a common assignee herewith. In that patent, the construction of the probe is specifically intended to optimize energy transfer by coupling the probe to the detected electromagnetic radiation at a location of lowest impedance in the waveguide.
A limitation of such a rotary probe signal receiver is that it can at one time pick up only one of the two orthogonally polarized modes of the typical satellite television signal. This means that only one half of the television channels available to the viewer may be processed at a time. This is undesirable where the number of viewers connected to the signal receiving system is high, e.g. with respect to a system for an apartment building. In addition, the motor for rotating the probe between the two polarized signal modes is subject to wear and tear and can be adversely affected by severe weather conditions.
There are numerous configurations of probes and waveguides having various dimensions and proportions, all intended to receive specific transmission frequencies and modes. Nevertheless, in view of the many different ways in which electromagnetic fields can be distributed within a waveguide, that is, the many different modes that are possible, and in view of the many different frequencies and polarization schemes that are proposed, there still remains the requirement to provide a waveguide pick-up for optimizing the reception of satellite transmissions, while minimizing cost and complexity.